1. Field of the Invention
The present invention relates to a switch whose opening and closing is controlled by pulses and the construction of such a switch in the form of an integrated circuit. The present invention is directed more particularly at power switches able to block relatively high voltages and permit the passage of high intensity currents.
2. Description of the Prior Art
At present solid state electronic switches for unidirectional currents are subdivided into three main groups. These groups will be analyzed hereinafter in connection with the control mode of the switch.
The first group comprises devices of the thyristor, gate amplification thyristor and similar types. For controlling the closing of such switches it is necessary to apply a current pulse to the gate thereof. The switch remains conductive as long as a voltage is applied between the main terminals thereof. Such switches cannot be opened simply when a voltage is applied to their terminals. For this purpose it is necessary to provide relatively complex forced switching circuits.
The second group comprises devices of the transistor or Darlington circuit transistor types. These devices are controllable for the opening and closing. For the control thereof it is necessary to apply a base current which must be maintained throughout the conduction period. For opening purposes it is merely necessary to nullify the base current. Devices of this second group have the advantage compared with those of the first group that they require no forced switching circuit for their opening. However, they have the disadvantage that the base current must be applied throughout the conduction period, which complicates the control circuit and leads to consumption in the latter. To limit the consumption in the case of a battery supply it is at present standard practice in Darlington transistor control circuits to use converters for limiting the supply voltage of the base current and thus reduce dissipation in the control circuit.
The third group comprises devices of the gate turn off thyristor type. For closing, such devices require a gate current pulse of reasonable amplitude and short duration. However, the opening of such devices involves the application of a very high amplitude gate current in the opposite direction and which is essentially of the same order of magnitude as the main current passing through the device.